1. Field of the Invention
The present invention relates to a close-wound coil formed by winding a wire spirally and closely over a predetermined length, and a medical treatment tool using the close-wound coil.
2. Description of the Related Art
Generally, a medical treatment tool inserted into a human body through an endoscope channel comprises a treatment section provided at a distal end, a control section provided at a proximal end, and a transmission member to transmit the operating force from the control section to the treatment section.
The transmission member is inserted into an elongated channel extended in an endoscope which is inserted into a winding tubular abdominal cavity, and required not only to withstand bending and compressing but to transmit the operating force from the control section to the treatment section.
Thus, as described in Jpn. Pat. Appln. KOKAI Publication No. 56-112221, a close-wound coil formed by winding a wire with a circular section spirally and closely over a predetermined length, is widely used as a force transmission member.
FIG. 42 schematically illustrates an example of a conventional medical treatment tool having such a close-wound coil as a force transmission member. As illustrated in the drawing, a medical treatment tool 100 comprises a treatment section 102 provided at a distal end, an operation section 106 provided at a proximal end, and a close-wound coil 104 which connects the operation section 106 and treatment section 102. An endoscope 200 to lead the medical treatment tool 100 into a human body is provided with an insertion part 202 to be inserted into a tubular cavity in the body, and a control section 206 at a proximal end. A channel 208 to insert the medical treatment tool 100 is formed in the insertion part 202. At the distal end of the insertion part 202, a bending section 204 that is bent by a control knob (not shown) provided in the control section 206 is provided.
There is one serious problem in a conventional close-wound coil. That is, as shown in FIG. 42, when the endoscope 200 is led into a winding tubular abdominal cavity and the insertion section 202 of the endoscope 200 is bent complexly, the close-wound coil 104 of the medical treatment tool 100 inserted into the channel 208 of the insertion section 202 is also bent complexly over a long distance. Thus, even if the operation section 106 is rotated and the rotation force is transmitted to the treatment section 102 through the close-wound coil 104 in order to change the position of the treatment tool 102, for example, the treatment tool 102 may not rotate as intended due to various factors concerning the close-wound coil 104. Particularly, in the state that the bending section 204 is curved at a large angle with a small radius of curvature, it is very difficult to transmit the rotation force proportionally to the treatment section 102 at the end of the bending section 204.
FIG. 43 shows schematically the rotation transmission performance of a conventional close-wound coil in the bent state shown in FIG. 42. As indicated by a solid line, in a conventional close-wound coil, even if the operation section 106 is rotated in the bent state shown in FIG. 42, a delay or skip (unevenness) occurs in the rotation of the close-wound coil 104, and the treatment section 102 cannot follow faithfully the rotation of the close-wound coil 104. Namely, as indicated by a dashed line in FIG. 43, it is ideal that the rotation angle (input angle) of the operation section 106 appears directly as a rotation angle (output angle) of the treatment section 102 (input angle=output angle), but actually as indicated by a solid line in FIG. 43, a delay occurs between the input angle and output angle due to a rotation delay or rotation skip (input angle−delay angle=output angle), and the rotation output is not stabilized and fine adjustment to a desired rotation angle is difficult.